Multiple route pre-calculation and presentation for a vehicle navigation system

ABSTRACT

A navigation system and related operating methods are provided for instructing an operator of a vehicle. The navigation system obtains a destination location and generates a proposed route to the destination location. The proposed route is defined by one or more driver decision points and associated driving maneuvers. Before the vehicle reaches an approaching driver decision point, the navigation system pre-calculates alternate routes between the approaching driver decision point and the destination location, and saves the alternate routes for subsequent activation. Pre-calculated alternate routes can also be used to determine and indicate the relative importance of an approaching driving maneuver. The driver can consider the importance of driving maneuvers when deciding whether or not to follow the recommended route.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally tovehicle navigation and route planning systems. More particularly,embodiments of the subject matter relate to a vehicle navigation systemthat pre-calculates alternate routes to a destination before the vehiclediverts from the currently calculated route.

BACKGROUND

The prior art is replete with different types of electronic navigationsystems. Some electronic navigation systems are handheld, and others arevehicle-based. A vehicle navigation system generally provides navigationinstructions, location data, and map information to the vehicleoperator. Some existing vehicle navigation systems attempt to optimize aroute based upon different factors. Route calculation is typicallyperformed by examining a number of possible paths, and selecting the“best” path according to a number of optimization rules. For instance,the shortest possible route may be chosen to minimize the distancetraveled or high-speed roads may be chosen to minimize travel time. Someadvanced navigation systems utilize real-time traffic congestion data inan attempt to guide the vehicle away from traffic jams. After theoptimization criteria have been selected, automated vehicle routeguidance is typically performed in a two-step process: (1) a proposedroute is calculated from a starting position of the vehicle to thedesired destination; and (2) guidance instructions are presented to thevehicle operator as the vehicle traverses the proposed route.

Many existing vehicle navigation systems will automatically calculate anupdated route whenever the vehicle diverts from the previouslycalculated route. For example, after the system detects that the vehiclehas turned at an intersection rather than proceed straight as originallydesignated, it will generate a new route to the destination, based uponthe current location of the vehicle. Recalculation of an alternate routecan take an appreciable amount of time (associated with thedetermination that the vehicle did not follow the original route, andwith the actual computation of the new route), which can be inconvenientand confusing for the driver.

Existing vehicle navigation systems annunciate and/or display guidanceinstructions to the driver in advance of the next approachingintersection, transition, turnoff, or driving maneuver. For example, asystem might display and audibly announce “Exit At Maynard Avenue” oneor more times as the vehicle approaches that turnoff. However, theinstruction “Exit At Maynard Avenue” in and of itself does not conveywhether or not the driver “MAY exit,” or “SHOULD exit,” or “MUST exit”at Maynard Avenue. In this context, if Maynard Avenue is the lastfreeway exit for twenty miles, then the instruction ought to be treatedas mandatory, important, or critical. On the other hand, if the drivercan easily backtrack to Maynard Avenue by taking the immediatelyfollowing freeway exit, then the instruction need not be treated asmandatory, important, or critical. Existing vehicle navigation systemsdo not alter or modulate the manner in which driving instructions arepresented as a function of the importance of the driving maneuvers.

BRIEF SUMMARY

A navigation method is provided for instructing an operator of avehicle. The method obtains a destination location, and generates aproposed route to the destination location. The proposed route isdefined by one or more driver decision points and associated drivingmaneuvers. Before the vehicle reaches an approaching driver decisionpoint, the method pre-calculates an alternate route between theapproaching driver decision point and the destination location. Next,the method saves the alternate route to obtain a saved alternate routefor subsequent activation.

Another navigation method for instructing an operator of a vehicle isalso provided. This method begins by generating a proposed route to adestination location. The method pre-calculates, before the vehiclereaches an approaching driver decision point of the proposed route, analternate route between the approaching driver decision point and thedestination location, wherein the alternate route is different than theproposed route. The proposed route is compared to the alternate route toobtain a route comparison, and the method continues by determining adifference metric value associated with the route comparison. Then, themethod presents, to the operator of the vehicle, indicia of theimportance of a driving maneuver associated with the approaching driverdecision point. The driving maneuver is recommended by the proposedroute, and content of the indicia is influenced by the differencemetric.

A navigation system is provided for instructing an operator of avehicle. The system includes a navigation processor and a displayelement. The navigation processor is configured to obtain a destinationlocation, and to generate a proposed route to the destination location.The proposed route is defined by one or more driver decision points andassociated driving maneuvers. The display element is coupled to thenavigation processor, and the display element is configured to render agraphical representation of at least one segment of the proposed route.Before the vehicle reaches an approaching driver decision point, thenavigation processor pre-calculates an alternate route between theapproaching driver decision point and the destination location. Thenavigation processor activates the alternate route when the vehiclediverts from the proposed route at the approaching driver decisionpoint.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the subject matter may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures.

FIG. 1 is a schematic representation of an embodiment of a vehiclenavigation system;

FIG. 2 is a diagram of a proposed driving route and alternate routesegments;

FIG. 3 is a flow chart that illustrates an embodiment of a multi-routenavigation process;

FIG. 4 is a flow chart that illustrates an embodiment of a multi-routepresentation process; and

FIG. 5 is a schematic representation of an exemplary display generatedby a vehicle navigation system.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Techniques and technologies may be described herein in terms offunctional and/or logical block components, and with reference tosymbolic representations of operations, processing tasks, and functionsthat may be performed by various computing components or devices. Itshould be appreciated that the various block components shown in thefigures may be realized by any number of hardware, software, and/orfirmware components configured to perform the specified functions. Forexample, an embodiment of a system or a component may employ variousintegrated circuit components, e.g., memory elements, digital signalprocessing elements, logic elements, look-up tables, or the like, whichmay carry out a variety of functions under the control of one or moremicroprocessors or other control devices.

For the sake of brevity, conventional techniques related to signalprocessing, image processing, data transmission, general vehiclenavigation system operation, and other functional aspects of the systems(and the individual operating components of the systems) may not bedescribed in detail herein. Furthermore, the connecting lines shown inthe various figures contained herein are intended to represent examplefunctional relationships and/or physical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical connections may be present in anembodiment of the subject matter.

When using a vehicle navigation system, drivers will sometimes deviatefrom a proposed route because they are aware of an alternate path, theydo not like the proposed route, they want to take a side trip, or forsome other reason. Traditionally, when a driver deviates from apredetermined route calculated by a navigation system, the system willannounce that it is recalculating the route in an attempt to direct thedriver back to the original route. Drivers tend to disable voice promptsof a vehicle navigation system to avoid being annoyed by recalculationprompts and related guidance instructions.

An embodiment of an electronic navigation system as described here canreduce or eliminate the bothersome experience associated with therecalculation of a proposed route, while still providing valuabledriving instructions that lead to the desired destination. The systemallows the driver to feel more in control by giving the driveralternatives at route nodes when appropriate, and by indicating to thedriver when a given route segment really should be followed. Certainembodiments of the navigation system will calculate alternate routescorresponding to each node or driver decision point along an originallyplanned route. Thus, when the driver misses a planned maneuver orchooses to take an alternate path, the system can automatically andquickly switch to the appropriate pre-calculated alternate route withoutdelay. This methodology provides useful alternate route information tothe driver in a seamless manner and without forcing the driver back tothe originally planned route. The system may also show the primary routeand one or more alternative routes, along with acceptable paths oftravel at each driver decision point, to give options to the driverrather than providing only one proposed route.

In certain embodiments, the navigation system need not calculate allpossible routes from a given driver decision point. Rather, the systemcould selectively calculate and store alternate routes that arerealistic and practical. For example, the system might selectivelyprocess alternate routes that do not add a significant or unreasonableamount of driving time or mileage to the originally planned route. Asanother example, the system need not compute alternate routes that wouldgenerally lead the vehicle away from the intended destination.

The vehicle navigation system could also calculate and process alternateroutes in advance to determine the relative importance or criticality ofapproaching maneuvers. In turn, the system can indicate to the driverwhether or not certain maneuvers are optional, highly recommended,mandatory, etc. In certain embodiments, when a given route instructionis calculated, one or more secondary routes are computed and analyzed todetermine what might happen if the driver misses the recommended routeinstruction. If a secondary route will significantly or noticeablyimpact the desired route (e.g., it adds fifteen miles to the commute),then the system will notify the driver of the relative importance of theapproaching maneuver. Such additional guidance will help the driverdecide whether to focus on or casually follow a given drivinginstruction.

The indication of relative importance can be conveyed to the driver in avariety of ways, including, without limitation: color coding; voiceprompt authoritativeness; voice prompt timing; a time difference; amileage difference; or the like. For example, if the vehicle istraveling on a highway and is supposed to exit before a bridge, then thesystem could inform the driver well in advance that the highway must beexited before the bridge, otherwise at least twenty minutes will beadded to the drive time.

Turning now to the figures, FIG. 1 is a schematic representation of anembodiment of a navigation system 100, which is suitably configured toinstruct an operator. For this example, the system 100 is deployedonboard a host vehicle, such as an automobile. In practice, the system100 may be implemented as part of an onboard vehicle navigation system,an onboard vehicle entertainment system, an onboard display system, anonboard vehicle instrumentation cluster, or the like. In otherembodiments, the system 100 may be implemented as a portable system orincorporated into a mobile device such as a mobile telephone, a personaldigital assistant, a video game device, or the like. The illustratedembodiment of the system 100 includes, without limitation: a displayelement 102; at least one speaker 104; a user interface 106; anavigation processor 108; and a suitable amount of memory 110. Inpractice, the various components of the system 100 are coupled togetherin a manner that facilitates the communication of data, instructions,control signals, and possibly other signals. In practice, the system 100may include additional components configured to perform conventionalfunctions that are unrelated to the subject matter described here.

Generally, the navigation processor 108 is configured to perform orotherwise support the various operations and functions described herein.The navigation processor 108 may include one processor device or aplurality of cooperating processor devices. Moreover, the navigationprocessor 108 may be implemented or performed with a general purposeprocessor, a content addressable memory, a digital signal processor, anapplication specific integrated circuit, a field programmable gatearray, any suitable programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationdesigned to perform the functions described here. A processor device maybe realized as a microprocessor, a controller, a microcontroller, or astate machine. Moreover, a processor device may be implemented as acombination of computing devices, e.g., a combination of a digitalsignal processor and a microprocessor, a plurality of microprocessors,one or more microprocessors in conjunction with a digital signalprocessor core, or any other such configuration.

The memory 110 accommodates the saving and storing of data, softwareprogram code, and other information used to support the operation of thesystem 100. The memory 110 may be realized as RAM memory, flash memory,EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. The memory110 can be coupled to other elements of the system 100 to support thereading of information from, and the writing of information to, thememory 110. In certain embodiments, the memory 110 is integral to thenavigation processor 108. For example, the navigation processor 108 andthe memory 110 may reside in an ASIC or be implemented with a system ona chip.

For this embodiment of the system 100, the navigation processor 108obtains location data 112 from an appropriate source that provides dataindicative of the current vehicle location or position. In one practicalembodiment, the location data source is realized as an onboard GPSreceiver/processor that derives the current geographic position of thevehicle from GPS data received by the vehicle in real-time orsubstantially real-time.

The navigation processor 108 is also configured to obtain map data 114from an appropriate source that provides data indicative of currentcartographic, topological, location, road, and possibly other datauseful to the system 100. The map data 114 can represent locally stored,cached, downloaded, or accessible information, which can be processed bythe navigation processor 108. For example, in a fully onboardimplementation, the map data source(s) may be realized as one or morehard disks, semiconductor memory devices, portable storage media, or thelike. In an alternate embodiment, the map data source(s) may be realizedas an onboard memory cache that temporarily stores the map data 114 thatis downloaded from remote databases.

The display element 102, the speaker(s) 104, and the user interface 106may be configured in accordance with conventional vehicle navigation,information, or instrumentation systems to enable onboard interactionwith the vehicle operator. The display element 102 may be a suitablyconfigured LCD, plasma, CRT, OLED, or head-up display, which may or maynot be utilized for other vehicle functions. In accordance with knowntechniques, an appropriate display driver of the system 100 can providerendering control signals to the display element 102 to cause thedisplay element 102 to render maps, proposed routes, roads, navigationdirection arrows, and other graphical representations, elements, orindicia as necessary to support the function of the system 100.

The speaker(s) 104 may be devoted to the system 100, may be realized aspart of the audio system of the vehicle, or may be realized as part ofanother system or subsystem of the vehicle. Briefly, speaker(s) 104 mayreceive audio signals from the navigation processor 108, where suchaudio signals convey navigation instructions, user prompts, warningsignals, and other audible signals as necessary to support the functionof the system 100.

User interface 106 is configured to allow the vehicle operator to enterdata and/or control the functions and features of the system 100. Forexample, the operator can manipulate the user interface 106 to enter astarting location and a destination location for the vehicle, where thestarting and destination locations are utilized by the system 100 forpurposes of route planning. If the desired starting location correspondsto the current vehicle location, then the operator need not enter thestarting location if the system 100 includes a source of current vehicleposition information. The user interface 106 may be realized using anyconventional device or structure, including, without limitation: akeyboard or keypad; a touch screen (which may be incorporated into thedisplay element 102); a voice recognition system; a cursor controldevice; a joystick or knob; or the like.

The system 100 can perform a number of navigation functions, operations,processes, and methods, which are described in more detail herein.Typically, the system 100 generates and presents guidance informationand instructions associated with a proposed or default route to adestination. In addition, the system 100 generates at least onealternate or secondary route in advance such that the alternate routecan be activated with little to no delay when needed.

FIG. 2 is a diagram of a proposed driving route 200 and alternate routesegments that lead to a destination location 202. The proposed drivingroute 200 includes five segments, which are separated by nodes or driverdecision points. In FIG. 2, the circles represent the different driverdecision points. As used here, a “driver decision point” is anylocation, position, intersection, landmark, waypoint, street name,measure of distance, on-ramp/off-ramp, or the like, that might be usedby the navigation system as a reference for providing route guidance.For example, a driver decision point may be associated with one of moreof the following instructions, without limitation: turn left or right;veer left or right; stay left or right; proceed straight; make a U-turn;exit or enter a road, highway, or freeway; stop; arrive at destination;or the like.

The proposed driving route 200 is defined by five driver decision points(the numbered circles in FIG. 2). For this example, prior to the firstdriver decision point 204 the navigation system might announce (audiblyand/or visually) an instruction to continue ahead or proceed straight onthe current path. Alternatively, since no driving maneuver is requiredat the first driver decision point 204, the navigation system couldremain silent at this point. The second driver decision point 206corresponds to an instruction to turn right, the third driver decisionpoint 208 is associated with an instruction to continue straight (or, insome embodiments, no instruction), the fourth driver decision point 210corresponds to an instruction to turn left, and the fifth driverdecision point 212 represents the destination location 202.

FIG. 2 also depicts two alternate routes that could be taken from thethird driver decision point 208. Either of these two alternate routescould result if the vehicle diverts from the original proposed drivingroute 200. For this example, if the vehicle turns left at the thirddriver decision point 208, then a first alternate route 220 may betaken. If, however, the vehicle makes a sharp left turn at the thirddriver decision point 208, then a second alternate route 230 may betaken. As depicted in FIG. 2, the first alternate route 220 results insome additional time and mileage relative to the proposed driving route200. On the other hand, the second alternate route 230 would result in asignificant amount of additional time and mileage. Thus, the firstalternate route 220 is preferred over the second alternate route 230. Asexplained in more detail herein, certain embodiments of a navigationsystem might provide information prior to the third driver decisionpoint 208, such that the driver can decide how best to maneuver thevehicle at that point.

FIG. 3 is a flow chart that illustrates an embodiment of a multi-routenavigation process 300. The process 300 may be performed by, forexample, the navigation system 100. The various tasks performed inconnection with the process 300 may be performed by software, hardware,firmware, or any combination thereof. For illustrative purposes, thefollowing description of the process 300 may refer to elements mentionedabove in connection with FIG. 1. In practice, portions of the process300 may be performed by different elements of the described system,e.g., the navigation processor, the memory element, the display element,or the like. It should be appreciated that the process 300 may includeany number of additional or alternative tasks, the tasks shown in FIG. 3need not be performed in the illustrated order, and the process 300 maybe incorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. Moreover, insome embodiments, one or more of the illustrated tasks may be omitted.

The multi-route navigation process 300 represents one exemplarytechnique for pre-calculating and storing one or more alternate routesto a destination location. Thus, the process 300 may begin by obtaininga starting location and a destination location for the vehicle (task302). The starting and destination locations may be utilized todetermine one or more potential routes or potential route sections to berecommended for travel to the destination location. Next, the process300 generates a proposed route to the destination location (task 304).As explained above with reference to FIG. 2, the proposed routegenerated during the task 304 can be defined by one or more driverdecision points, along with their associated driving maneuvers. Thisproposed route can be saved for use as the default route. In someembodiments, the process 300 may generate more than one proposed routefor selection by the vehicle operator. The process 300 will providenavigation instructions corresponding to the currently active route tothe vehicle operator in an ongoing manner, as is understood by thosefamiliar with vehicle/portable navigation systems. The navigationinstructions may be realized as graphical reminders, audible warnings orinstructions, a printed map indicating the proposed route, or the like.

In contrast to conventional navigation systems that compute alternateroutes only when necessary (i.e., after the vehicle has diverted fromthe currently active navigation route), a navigation system thatexecutes the multi-route navigation process 300 pre-calculates at leastone alternate route to the destination location (task 306). Thispre-calculation occurs some time before the vehicle reaches anapproaching driver decision point, e.g., the next driver decision point.The alternate route provides driving instructions and guidance betweenthe approaching driver decision point and the destination location, andthe alternate route is different than the corresponding portion of theproposed route. In certain embodiments, an alternate route for the nextapproaching driver decision point is pre-calculated when the vehicle isnear, has passed, or has satisfied the driving maneuver for, the lastdriver decision point. In other embodiments, an alternate route for anapproaching driver decision point can be pre-calculated at any timebefore the vehicle reaches that point, for example, two or more driverdecision points ahead of time.

Pre-calculation of alternate routes considers one or more of thepossible ways that the vehicle might divert from the currently activeroute at the approaching driver decision point. For instance, if thedefault route instructs the driver to veer left at a fork in the road,then the task 306 will pre-calculate one or more alternate routes thatassume the vehicle instead veers right. As another example, if thedefault route instructs the driver to proceed straight at a four-wayintersection, then the task 306 will pre-calculate at least onealternate route that assumes the vehicle turns right, at least onealternate route that assumes the vehicle turns left, and possibly atleast one alternate route that assumes the vehicle makes a U-turn. Inpractice, the task 306 need not completely re-calculate the route to thedestination location. Rather, the task 306 could merely re-calculate apath that brings the vehicle back to a driver decision point that isincluded in the original proposed route.

After pre-calculating one or more alternate routes, the multi-routenavigation process 300 can save the alternate route(s) for subsequentactivation (task 308). Thus, alternate routes can be stored for quickand virtually immediate activation if necessary. Such pre-calculationand saving of alternate routes enhances the user experience of thenavigation system, and reduces or eliminates delay that is normallyassociated with on-the-fly dynamic route recalculation.

The multi-route navigation process 300 need not pre-calculate each andevery possible alternate route to the destination location. In thisregard, the process 300 could implement a filtering or selection schemethat limits pre-calculation of alternate routes to a manageable,reasonable, and realistic number, and/or that limits pre-calculation ofalternate routes to those that result in less impact on the commute.Thus, the process 300 could compare a plurality of potential routes tothe proposed route, and select or prioritize the potential routes in amanner that is influenced by the comparison. Such selectivity orpriority may be influenced by any appropriate metric that indicates adifference between the originally planned route and an alternate route.In this regard, a difference metric could be a metric such as, withoutlimitation: a distance metric; a travel time metric; a trafficcongestion metric; a fuel consumption metric; an energy consumptionmetric; a vehicle emissions metric; a road condition metric; asightseeing metric; an undesirable area metric; a services (restaurants,hotels, gas, etc.) metric; a preferred route metric; a metric related topast user behavior at the driver decision point; or any combinationthereof. In practice, a potential route might be selected forconsideration if its respective difference metric satisfies a thresholdcriteria. For example, the process may favor alternate routes that addless than a threshold amount of time to the originally planned routeand/or alternate routes that add less than a threshold distance to theoriginally planned route. As another example, the process may disregardalternate routes that might lead the vehicle onto single lane roads.

Although the multi-route navigation process 300 pre-calculates and savesone or more alternate routes, an alternate route need not be activatedor executed until needed. In other words, the navigation system can saveand update alternate routes until it detects that the vehicle hasdiverted from its currently designated route. This allows the system toquickly switch to a different route without having to compute the newroute on the fly.

The exemplary embodiment described here pre-calculates and updates itsalternate routes when the vehicle is near a driver decision point. Incertain embodiments, the navigation system pre-calculates one or morealternate routes for the next approaching driver decision point afterthe vehicle passes the immediately preceding driver decision point. Inother words, after the vehicle passes one driver decision point, thenavigation system pre-calculates at least one alternate route for thenext driver decision point. Accordingly, the illustrated embodiment ofthe process 300 detects when the vehicle is near, at, or past a driverdecision point (query task 310). If so, then the process 300 will alsocheck whether the vehicle has diverted from the proposed route at thatdriver decision point (query task 312). In practice, query task 312checks whether the vehicle has performed the predetermined anddesignated driving maneuver associated with the current driver decisionpoint.

If the process 300 detects that the vehicle has diverted from theproposed route, then the navigation system activates a saved alternateroute (task 314). Thereafter, the navigation system continues with thecurrently activated route (task 316). Moreover, since query task 310 hasdetected that the vehicle is near, at, or past a driver decision point,the process 300 pre-calculates at least one updated alternate route.This updating will be associated with the next approaching driverdecision point, resulting in one or more potential alternate routes thatmight be taken by the vehicle at that next point. After pre-calculatingthe updated alternate route(s), the process 300 may return to task 308to save those route(s).

If query task 312 determines that the currently activated route wasfollowed, then the process 300 leads to task 312 and continues asdescribed above. Thus, the current route remains active, and the process300 proceeds to pre-calculate the next possible alternate routes. Themulti-route navigation process 300 may continue in this manner until thevehicle reaches the destination location, and any number of alternateroutes may be pre-calculated in a dynamic manner as the vehicle drivesto the destination location.

The pre-calculation and saving of alternate routes enables thenavigation system to present useful information to the driver as thevehicle travels to the destination location. In this regard, FIG. 4 is aflow chart that illustrates an embodiment of a multi-route presentationprocess 400. The process 400 may be performed by, for example, thenavigation system 100. The various tasks performed in connection withthe process 400 may be performed by software, hardware, firmware, or anycombination thereof. For illustrative purposes, the followingdescription of the process 400 may refer to elements mentioned above inconnection with FIG. 1 and FIG. 3. In practice, portions of the process400 may be performed by different elements of the described system,e.g., the navigation processor, the memory element, the display element,or the like. It should be appreciated that the process 400 may includeany number of additional or alternative tasks, the tasks shown in FIG. 4need not be performed in the illustrated order, and the process 400 maybe incorporated into a more comprehensive procedure or process havingadditional functionality not described in detail herein. In this regard,the process 400 may be combined with the process 300, or the twoprocesses may be executed in parallel. Moreover, in some embodiments,one or more of the illustrated tasks may be omitted.

The multi-route presentation process 400 assumes that one or morealternate routes (corresponding to the next approaching driver decisionpoint) have been pre-calculated and saved, as explained above. Forsimplicity and ease of description, this embodiment of the process 400assumes that one alternate route has been pre-calculated and saved.Accordingly, the process 400 begins by comparing the proposed route tothe alternate route (task 402). The resulting route comparison can beused to determine one or more applicable difference metric values (task404) that indicate some practical difference between the two routes. Thedifference metric used here may be related to or otherwise associatedwith any of the following, without limitation: driving distance; traveltime; traffic congestion; fuel consumption or economy; energyconsumption or economy; vehicle emissions; road condition; sightseeingcontent; the preference or status of the area; available services(restaurants, hotels, gas, etc.); the preference or status of the route;past user behavior at the driver decision point; or any combinationthereof.

In some embodiments, the process 400 displays at least one segment orsection of the proposed route in one way, and displays at least onesegment or section of the alternate route in a different way, tovisually distinguish the proposed route from the alternate route. Forexample, the proposed route may be rendered using first visuallydistinguishable characteristics and the alternate route may be renderedusing second visually distinguishable characteristics (task 406). Inthis regard, the different visually distinguishable characteristics maycorrespond to any of the following characteristics, individually or inany combination thereof: different colors; different brightness;different transparency levels; different translucency levels; differentline patterns; different line thickness; different shapes; differentsizes; different flicker patterns; different focus levels; differentsharpness levels; different clarity levels; different texturing;different shadowing; varying animations that might depict the relativetime/speed of the alternate route; or the like.

The different visually distinguishable characteristics used forrendering route segments may be coded or otherwise selected such thatthey convey something meaningful and contextually relevant. Moreover,the contextual meaning may be correlated to the difference metricdetermined during task 404. For example, the proposed route may berendered in a highlighted manner or by using a specific color such asgreen, while the alternate route may be rendered in a subdued manner orby using a contrasting color such as amber. In this regard, FIG. 5 is aschematic representation of an exemplary display 500 generated by avehicle navigation system. The display 500 is a simplified depiction ofa segment of a proposed route 502, along with a segment of a firstalternate route 504 and a segment of a second alternate route 506. Forthis example, the proposed route 502 calls for the vehicle to continuestraight through an intersection 508. The first alternate route 504assumes that the vehicle turns left at the intersection 508, and thesecond alternate route 506 assumes that the vehicle turns right at theintersection 508. FIG. 5 schematically depicts three different visuallydistinguishable characteristics for the proposed route 502 (e.g., afirst color, such as green or white), the first alternate route 504(e.g., a second color represented by the cross hatching, such as red),and the second alternate route 506 (e.g., a third color represented bythe stippling, such as amber). The first alternate route 504 may bedisplayed in red as an indication that it is not a preferred ordesirable route. On the other hand, the second alternate route 506 maybe displayed in amber as an indication that it is an appropriate oracceptable route.

Referring again to FIG. 4, the multi-route presentation process 400 mayalso present (display or announce) to the operator of the vehicle someindicia of the difference metric associated with the alternate routeunder consideration (task 408). In this regard, different visuallydistinguishable characteristics (as described above) can be consideredto be displayable indicia to the extent they convey meaning that isunderstandable by the operator. In certain embodiments, however, visibleindicia (text, labels, icons, or the like) of the difference metric isdisplayed along with at least one segment of the alternate route. FIG. 5depicts one possible implementation that employs text boxes that containone or more difference metric values for the alternate routes. Forexample, the first alternate route 504 is displayed with a text box 510that includes an indication of the estimated additional driving distance(forty miles) and the estimated additional driving time (two hours) thatwill be experienced if the vehicle is diverted to the first alternateroute 504 along the way to the destination location. The secondalternate route 506 is displayed with a text box 512 that includes anindication of the estimated additional driving distance (five miles) andthe estimated additional driving time (fifteen minutes) that will beexperienced if the vehicle is diverted to the second alternate route 506along the way to the destination location.

In certain embodiments, the calculated difference metric is analyzed andcompared to a threshold value (query task 410). The threshold valuemight correspond to a tolerable or acceptable amount of inconvenience,additional time, additional distance, etc., and the threshold valuecould be selected or configured by the user. This threshold value isused by the navigation system to determine the relative importance,criticality, desirability, or priority of the upcoming driving maneuverthat is associated with the approaching driver decision point. Forexample, the threshold value may be defined to be a predetermineddistance (such as ten miles), a predetermined amount of time (such asthirty minutes), a predetermined measure of fuel consumption (such as agallon of gasoline), or the like. Moreover, the threshold value maycontemplate any appropriate criteria, including a combination ofdifferent criteria. For example, the threshold value may contemplatetravel time, distance, and/or fuel efficiency. Thus, there could be anynumber of factors that are considered when determining the relativeimportance of the upcoming navigation maneuver. The embodiment depictedin FIG. 5 assumes that a lower difference metric value is preferred overa higher difference metric value. In other embodiments, of course, theopposite may hold (depending upon the particular metric used).

For this example, if the computed difference metric value does notexceed the threshold value, then the multi-route presentation process400 presents indicia of an approaching “low importance” or “optional” or“low priority” driving maneuver (task 412). On the other hand, if thecomputed difference metric value exceeds the threshold value, then theprocess 400 presents indicia of an approaching “high importance” or“mandatory” or “high priority” driving maneuver (task 414). In eithercase, the content of the indicia (whether displayed and/or announced)will be responsive to, or otherwise influenced by, the calculateddifference metric value. Although this example relates to an embodimenthaving two different priority or importance levels, the number ofpriorities or levels need not be limited to only two. In this regard, anavigation system and the process 400 could be suitably configured tosupport three (low/intermediate/high) or more priorities.

The navigation system can indicate the importance or criticality of arecommended driving maneuver in any number of ways. For example, thesystem may render route segments using visually distinguishablecharacteristics that are coded to indicate the importance of a drivingmaneuver (see FIG. 5). Thus, if an alternate route segment would add asignificant amount of time or distance to the trip, then that alternateroute segment may be colored red to indicate that it should be avoided.Alternatively (or additionally), the difference metric value or valuesthemselves may be presented (see FIG. 5) so that the driver canappreciate the actual impact an alternate route might have on thecommute. Alternatively (or additionally), graphical icons or symbolscould be used to indicate the importance of a given driving maneuver. InFIG. 5, for example, the proposed route 502 is identified using a simplearrow 520. In contrast, the first alternate route 504 is identifiedusing a visibly distinguishable arrow 522 that indicates an undesirableroute. The second alternate route 506 is identified using yet anothertype of arrow 524 that indicate an acceptable route.

The importance, criticality, or nature of an approaching drivingmaneuver could also be indicated with a different annunciation ordisplay scheme. For example, if the next driver decision point (and itscorresponding driving maneuver) has little or no acceptable alternateroutes associated therewith, then the process 400 could provide anappropriate warning well in advance, display or announce that the nextdriving maneuver should be treated as mandatory, and/or present theassociated driving instruction in an assertive or authoritative tone. Incontrast, if all of the possible alternate routes associated with thenext driver decision point are acceptable (e.g., none of them would addsignificant time or distance to the commute), then the process 400 neednot take any special action, it may display or announce that the nextdriving maneuver can be treated as optional, and/or present theassociated driving instruction in a less assertive or less authoritativetone. Moreover, the frequency of announcements and/or the amount of leadtime given before the upcoming driver decision point may be influencedby the relative importance of the next driving maneuver. Thus, if theapproaching maneuver is considered mandatory, then the driver may bereminded more often and with plenty of lead time. As yet anotherexample, the assertiveness of the navigation system could vary dependingupon the relative importance of the maneuver. Thus, important maneuverscould preempt certain system applications/tasks to inform the user ofthe approaching maneuver, while relatively unimportant maneuvers mighthave no preemptive impact. Moreover, the navigation system could employdifferent animated turn indications and/or driving instructions, oremploy different voice prompt volume levels in a modulated manner thatis influenced by the relative importance of the approaching maneuver.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. It should also be appreciated that theexemplary embodiment or embodiments described herein are not intended tolimit the scope, applicability, or configuration of the claimed subjectmatter in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope defined by theclaims, which includes known equivalents and foreseeable equivalents atthe time of filing this patent application.

1. A navigation method for instructing an operator of a vehicle, themethod comprising: obtaining a destination location; generating aproposed route to the destination location, the proposed route definedby one or more driver decision points and associated driving maneuvers;and before the vehicle reaches an approaching driver decision point,pre-calculating an alternate route between the approaching driverdecision point and the destination location, wherein the alternate routeis different than the proposed route; and saving the alternate route toobtain a saved alternate route for subsequent activation.
 2. The methodof claim 1, further comprising detecting when the vehicle is near acurrent driver decision point of the proposed route, whereinpre-calculating the alternate route is triggered in response to thedetecting step.
 3. The method of claim 2, wherein the current driverdecision point immediately precedes the approaching driver decisionpoint in the proposed route.
 4. The method of claim 1, furthercomprising: detecting when the vehicle has diverted from the proposedroute at the approaching driver decision point; and activating the savedalternate route in response to the detecting step, resulting in anactivated alternate route.
 5. The method of claim 4, further comprising:pre-calculating an updated alternate route between a next approachingdriver decision point of the activated alternate route and thedestination location, wherein the updated alternate route is differentthan the activated alternate route; and saving the updated alternateroute to obtain a saved updated alternate route for subsequentactivation.
 6. The method of claim 1, further comprising: displaying atleast one segment of the proposed route using first visuallydistinguishable characteristics; and displaying at least one segment ofthe alternate route using second visually distinguishablecharacteristics that are different than the first visuallydistinguishable characteristics.
 7. The method of claim 1, furthercomprising: comparing the proposed route to the alternate route toobtain a route comparison; determining a difference metric valueassociated with the route comparison; and displaying at least onesegment of the alternate route, along with indicia of the differencemetric.
 8. The method of claim 7, wherein the difference metriccomprises a metric selected from the group consisting of: a distancemetric; a travel time metric; a traffic congestion metric; a fuelconsumption metric; an energy consumption metric; a vehicle emissionsmetric; a road condition metric; a sightseeing metric; an undesirablearea metric; a services metric; a preferred route metric; and a metricrelated to past user behavior at the driver decision point.
 9. Themethod of claim 1, further comprising: pre-calculating a plurality ofpotential routes between the approaching driver decision point and thedestination location, the potential routes including the alternateroute, and each of the potential routes being different than theproposed route; comparing each of the potential routes to the proposedroute; and determining, in response to the comparing step, a respectivedifference metric value for each of the potential routes; wherein thedifference metric for the alternate route satisfies a thresholdcriteria.
 10. The method of claim 9, wherein the difference metriccomprises a metric selected from the group consisting of: a distancemetric; a travel time metric; a traffic congestion metric; a fuelconsumption metric; an energy consumption metric; a vehicle emissionsmetric; a road condition metric; a sightseeing metric; an undesirablearea metric; a services metric; a preferred route metric; and a metricrelated to past user behavior at the driver decision point.
 11. Anavigation method for instructing an operator of a vehicle, the methodcomprising: generating a proposed route to a destination location;pre-calculating, before the vehicle reaches an approaching driverdecision point of the proposed route, an alternate route between theapproaching driver decision point and the destination location, whereinthe alternate route is different than the proposed route; comparing theproposed route to the alternate route to obtain a route comparison;determining a difference metric value associated with the routecomparison; and presenting, to the operator of the vehicle, indicia ofthe importance of a driving maneuver associated with the approachingdriver decision point, wherein the driving maneuver is recommended bythe proposed route, and wherein content of the indicia is influenced bythe difference metric.
 12. The method of claim 11, further comprising:detecting when the vehicle has not performed the driving maneuver; andactivating the alternate route in response to the detecting step,resulting in an activated alternate route.
 13. The method of claim 11,further comprising: displaying at least one segment of the proposedroute using first visually distinguishable characteristics; anddisplaying at least one segment of the alternate route using secondvisually distinguishable characteristics that are different than thefirst visually distinguishable characteristics.
 14. The method of claim11, wherein the difference metric comprises a metric selected from thegroup consisting of: a distance metric; a travel time metric; a trafficcongestion metric; a fuel consumption metric; an energy consumptionmetric; a vehicle emissions metric; a road condition metric; asightseeing metric; an undesirable area metric; a services metric; apreferred route metric; and a metric related to past user behavior atthe driver decision point.
 15. The method of claim 11, furthercomprising comparing the difference metric value to a threshold value,wherein the presenting step comprises: presenting indicia of a lowimportance driving maneuver when the difference metric value is lessthan the threshold value; and presenting indicia of a high importancedriving maneuver when the difference metric value is greater than thethreshold value.
 16. The method of claim 15, wherein: the differencemetric value represents additional driving distance to the destinationlocation, the additional driving distance being associated with thealternate route; and the threshold value is a predetermined distance.17. The method of claim 15, wherein: the difference metric valuerepresents additional driving time to the destination location, theadditional driving time being associated with the alternate route; andthe threshold value is a predetermined amount of time.
 18. A navigationsystem for instructing an operator of a vehicle, the system comprising:a navigation processor configured to obtain a destination location, andto generate a proposed route to the destination location, the proposedroute defined by one or more driver decision points and associateddriving maneuvers; and a display element coupled to the navigationprocessor, the display element configured to render a graphicalrepresentation of at least one segment of the proposed route; wherein:before the vehicle reaches an approaching driver decision point, thenavigation processor pre-calculates an alternate route between theapproaching driver decision point and the destination location; and thenavigation processor activates the alternate route when the vehiclediverts from the proposed route at the approaching driver decisionpoint.
 19. The system of claim 18, wherein: the navigation processorcompares the proposed route to the alternate route to obtain a routecomparison; the navigation processor determines a difference metricvalue associated with the route comparison; and the display elementdisplays at least one segment of the alternate route, along with indiciaof the difference metric.
 20. The system of claim 18, wherein: thenavigation processor compares the proposed route to the alternate routeto obtain a route comparison; the navigation processor determines adifference metric value associated with the route comparison; and thedisplay element displays indicia of the importance of a proposed drivingmaneuver associated with the approaching driver decision point, whereinthe proposed driving maneuver is included in the proposed route, andwherein content of the indicia is influenced by the difference metric.